The present invention relates to negative-resistance devices, and more particularly to interactive negative-resistance multistate devices.
Negative resistance devices have been of fundamental importance in the development of electronic apparatus of all types, and have long been the subject of both mathematical and experimental investigations.
There are basically two types of negative-resistance devices, categorized by the voltage-current behavior they exhibit. When voltage (ordinate) across the device is plotted as a function of current (abscissa) through the device, the first type exhibits a characteristic which is generally in the shape of an S. This class of device is also known as the short-circuit stable, or voltage-controlled type. The other type exhibits a characteristic generally shaped as an N, giving rise to the name N type-device. These N-type devices are also known as open-circuit stable, or current-controlled device.
Many negative-resistance devices exist in each category of devices. The S-type devices include, for example, the Hole Storage Transistor, the Tunnel Diode, and the Dynatron. Devices such as the Amorphous Semiconductor Diode, the Transitron, and the Avalanche Diode are all examples of N-type devices. It is well known that the negative-resistance mechanism of each of these devices is attributable to a different physical phenomena.
One particularly important and well known aspect of negative-resistance devices is that they may be connected together to form a composite device having multiple stable states. In fact, it has been shown that by combining a number M of these negative-resistance devices, a number of (M+1) stable states can be achieved. The existence of more then two (i.e., binary) stable states in a device is obviously important in many electronic applications, for example, a computer memory or logic. A device having four stable states rather than just two stable states clearly will store more information or can be used to process data more quickly and with fewer devices at lower cost and volume with increased reliability.
Arrangements and interconnection of negative-resistance devices to yield a multistate stable device are known to persons skilled in the electronic art. I discuss these negative-resistance devices in previous patents issued to me (including U.S. Pat. Nos. 3,333,196; 3,293,453; 3,089,039; 3,200,266; 3,184,602; 2,939,965). For example, in my U.S. Pat. No. 3,089,039, I disclose a multistable circuit which employs a plurality of negative-resistance devices (each exhibiting a short-circuit-stable negative-resistance characteristic) connected in series to give a composite multistable characteristic. In my article entitled "Variable Radix Multistable Integrated Circuits" published in the September, 1974 issue of "COMPUTER", by the IEEE Computer Society of the Institute of Electrical and Electronics Engineers, hereby incorporated by reference, I have described in experimental and mathematical terms both the theory and operation of these multistable devices resulting from interconnection of noninteracting negative-resistance devices.
Obviously, providing a way of interconnecting these negative-resistance devices in a manner to achieve additional stable states would be highly desirable. Negative-resistance devices have been well-known for many years; more recently, it has been commonly accepted that a combination of M devices to form a multistate stable device will produce at most M + 1 multistate stable stages. The present invention is intended to change that state of affairs, and to provide a multistate stable device by interconnecting the M negative-resistance devices to produce a minimum (M+1)+[(M-1)!] stable states--thus yielding an additional [(M-1)!] stable states.